Emergence of a nephropathogenic avian infectious bronchitis virus with a novel genotype in India

We describe the emergence of a nephropathogenic avian infectious bronchitis virus (IBV) with a novel genotype in India. The Indian IBV isolate exhibited a relatively high degree of sequence divergence with reference strains. The highest homology was observed with strain 6/82 (68%) and the least homology with strain Mex/1765/99 (34.3%).     

Sequence of the spike protein of the Belgian B164S isolate of nephropathogenic infectious bronchitis virus

The sequence of the gene encoding the spike glycoprotein (S) of the 1984 Belgian nephropathogenic isolate B1648 has been determined and shown to encode a protein of 1171 amino acids. Comparison of the deduced amino acid sequence of the S1 (amino-terminal half) of S, which induces virus-neutralizing antibodies, with that of vaccinal strains D274, H120 and D1466 revealed that it differed from them by 21, 25 and 49%, respectively, and by 24 to 25% from the North American nephropathogenic isolates Gray and Holte. The deduced amino add sequence of the S2 (carboxy-terminal) half of S differed by 10 to 12% (25% from D1466).     

Increased level of protection of respiratory tract and kidney by combining different infectious bronchitis virus vaccines against challenge with nephropathogenic Brazilian genotype subcluster 4 strains

Genotyping of seven infectious bronchitis virus (IBV) strains isolated in Brazil showed that all belonged to the common Brazilian genotype and that these strains were closest to the subcluster of strain IBV/Brazil/2007/USP-19. Pathotyping of four selected Brazilian strains showed that they all caused a considerable level of ciliostasis in the trachea but at a somewhat lower level than did M41 and Brazilian strains 50/96, 57/96, 62/96 and 64/96 representing four different serotypes that had been reported earlier. In contrast to the M41 challenge strain, all Brazilian isolates replicated in kidney tissue in a high percentage of non-vaccinated challenged birds, clearly showing that they are nephropathogenic. As for the tracheal protection, the results using Massachusetts (Mass) vaccination against the recent strains seemed to show protection higher on average than for the strains reported earlier. A single or twofold vaccination with a Mass vaccine resulted in a mean tracheal protection level against the four challenge strains of 92% and 90%, respectively, whereas a single and twofold vaccination with a Mass vaccine halved the percentage of infected kidneys (14% and 13%, respectively, P?P?相似文献   

Epitopes on the spike protein of a nephropathogenic strain of infectious bronchitis virus

Summary Infectious bronchitis virus (IBV), the first coronavirus described, was initially associated with severe respiratory disease. However, outbreaks have more recently also been associated with nephropathogenesis. Topographically interrelated antigenic determinants of the nephropathogenic Gray strain of IBV were characterized using eleven monoclonal antibodies (MAbs). Four MAbs (IgG 2a) defined epitopes that were both conformation-independent and group specific, reacting with Gray, Arkansas (Ark), and Massachusetts 41 (Mass 41) strains. Seven MAbs (IgG 1) defined conformation-dependent epitopes that could differentiate the Gray from the Ark and Mass strains. The spike protein specificity of the MAbs was determined with the conformation-independent MAbs and one MAb that reacted only in non-denaturing western blot assays. Competitive binding studies using these MAbs suggested a high degree of functional dependency among the associated epitopes as might be expected with a protein of complex secondary and tertiary structure. At least two regions associated with complete protection of infected embryos were identified that consisted of both conformation-dependent and independent epitopes. However, a non-neutralizing MAb, which did not protect the embryo from gross lesions, did inhibit virus-induced lesions and replication in the kidneys. These MAbs should be valuable tools in studying IBV pathogenesis.     

Phylogenetic analysis of avian infectious bronchitis virus strains isolated in Japan

Summary To define the origin and evolution of recent avian infectious bronchitis virus (IBV) in Japan, a genetic analysis was performed. By phylogenetic analysis based on the S1 gene including the sequence of the hypervariable regions, IBV isolates in Japan were classified into five genetic groups, which included two already-known groups (Mass and Gray). Among them, three major genetic groups were associated with the recent outbreaks of IB in Japan. One group is indigenous to Japan and could not be placed within the known existing groups in other countries. The remaining two groups, which have emerged recently, are related to isolates in China and Taiwan.     

Protection of chickens against renal damage caused by a nephropathogenic infectious bronchitis virus

The ability of the infectious bronchitis (IB) Ma5 and 4/91 live-attenuated vaccines to protect against kidney damage caused by a nephropathogenic strain of IB virus (B1648) was investigated. Protection parameters considered were gross and microscopic renal pathology, and the use of a polymerase chain reaction to detect IB RNA in kidney tissue. By each parameter, Ma5 vaccine alone provided poor protection, but 4/91 alone or the combined program both protected well.     

Vaccination of chickens against a Belgian nephropathogenic strain of infectious bronchitis virus B1648 using attenuated homologous and heterologous strains

White Leghorn chicks without and with maternally derived antibodies (MDA) to infectious bronchitis virus (IBV) and broiler chicks with MDA were vaccinated at 1 day of age either with H120 vaccine, combined H120 and D274 vaccines or with a non-commercial attenuated strain derived from the virulent Belgian nephropathogenic IBV strain, B1648. Protection following challenge with virulent B1648 was assessed 4 weeks later by virus isolation from the trachea, antigen detection in the kidney by immunofluorescence and mortality rates. Vaccination with either homologous or heterologous vaccines reduced the duration of virus replication in the trachea of all groups compared to unvaccinated controls. Homologous vaccination reduced the incidence of virus replication in the kidney. Heterologous vaccination (H120 to D274) did not reduce kidney infection in the MDA + groups; however, partial kidney-protection was found in the MDA - group. There was no correlation between serum antibody titres measured by ELISA and the degree of kidney protection.     

Antigenic variation in strains of avian infectious bronchitis virus

Summary Fifteen british field strains of IBV were compared using cross serum neutralization tests in embryonated eggs with seven standard reference strains of IBV. While the British field strains were considered to form a relatively homogeneous group considerable antigenic variation did occur. It was considered that it was not feasible at this time to describe accurately a serotype classification for IBV, similar to that described for other virus groups.     

Sequence analysis of infectious bronchitis virus isolates from the 1960s in the United States

To better understand the molecular epidemiology of infectious bronchitis virus (IBV) in the United States following the introduction of commercial IBV vaccines, we sequenced the S1 and N structural protein genes of thirteen IBV field isolates collected in the 1960s. Analysis of the S1 sequence showed that seven isolates were of the Massachusetts (Mass) genotype, five were SE17, and one was of the Connecticut (Conn) genotype, suggesting that these three IBVs were circulating in commercial poultry raised in different regions in the United States during the 1960s. The S1 genes of Mass-type isolates had high levels of sequence variation, representing 81.3-81.9 % nucleotide (nt) and 77.3-78.7 % amino acid (aa) identity when compared to those of the SE17-type isolates. In contrast, the N genes from the same isolates were less variable (>92 % nt and >93 % aa identity) when compared to those of the SE17-type isolates. Phylogenetic analysis based on the S1 gene indicated that one isolate (L748) was more closely related to the Mass type. In contrast, phylogenetic analysis based on the N gene showed that L748 was more closely related to the SE17 type, indicating that there had been exchange of S1 genetic materials between Mass- and SE17-like viruses. In addition, the Mass-type isolates had high levels of sequence identity in the S1 gene compared with widely used modified live vaccines (Mass41, Ma5 and H120) and modern field strains from the USA and other countries, suggesting a common ancestor.     

Characterisation of strains of infectious bronchitis virus isolated in Chile

Nine isolates of infectious bronchitis (IB)-like viruses were made from 23 flocks (broilers or layers) in Chile experiencing the types of disease problems commonly associated with IBV. Their identity as IB viruses was confirmed. The histological changes they caused in tracheal organ cultures (OC) are described. Serum neutralisation tests performed in embryonated eggs (alpha-method) suggested that four of the isolates were serologically related to the Massachusetts (Mass) serotype of IBV and one to Connecticut. The four other strains were examined further by a serum neutralisation test in OC (ss-method). One was found to be of the Mass serotype but the others were found to be unrelated antigenically to a wide range of IBV serotypes isolated in many countries over a number of years. One of these three strains and the Mass strain, when given intranasally to 8-day-old specified pathogen free chickens together with pathogenic serotypes of E.coli, caused some mortality and considerable morbidity. The H120 vaccine strain was found not to protect completely against challenge with these four strains 21 days later.     

Pathogenicity of Australian strains of avian infectious bronchitis virus

The pathogenicity of 25 strains of infectious bronchitis virus (IBV) isolated in Australia between 1961 and 1994 was compared in white leghorn specific pathogen-free chicks. Twelve strains were nephropathogenic and 10 respiratory, the other three being of mixed pathogenicity. The IBV strains identified as nephropathogenic induced clinical nephritis, gross and histological kidney lesions, and mortality of 5-90%. According to the severity of these features, the nephropathogenic strains could be further subdivided into strains of high, moderate or low pathogenicity. The three strains of mixed pathogenicity induced tracheitis, mild clinical nephritis and kidney lesions but no mortality. The 10 respiratory strains caused histological lesions in the trachea but not in the kidney, and did not induce clinical nephritis or mortality. Of 12 IBV strains isolated between 1961 and 1976, nine were nephropathogenic, inducing mortality of 15-90%. In contrast, of 13 strains isolated between 1981 and 1994, only three were nephropathogenic, inducing mortality of 5-37%, whereas nine were respiratory. Seven of these nine strains, unlike other respiratory strains, failed completely to replicate in the kidney. The results indicated a change in the prevalent IBV strains from highly nephropathogenic (1960s to 1970s) to respiratory (1980s to early 1990s); moreover, the late 1980s saw the emergence of respiratory strains with altered tissue tropism.     

Genetic analysis revealed LX4 genotype strains of avian infectious bronchitis virus became predominant in recent years in Sichuan area,China

Between 2008 and 2010, 19 strains of infectious bronchitis virus (IBV) were isolated from the vaccinated chicken flocks in Sichuan province, China. The S1 genes of the isolates were amplified and sequenced. Phylogenetic analysis revealed that the 19 isolates and 37 reference IBV strains can be grouped into eight genotypes. Although IBVs of Taiwan-I type, massachusetts type, and proventriculitis type were isolated, but most isolates were LX4 genotype. Homology analysis of the sequences of S1 genes of the 19 isolates and 37 reference IBV strains revealed that the identity of the nucleotides and amino acid sequences of the S1 genes between the 15 LX4-type isolates and other IBV strains were 71.9–99.3% and 72.1–99.1%, respectively, while those of the analyzed IBV of LX4 type were 96.0–99.9% and 94.3–99.8%, respectively. The results from this study and other published results in the GenBank database showed that isolates circulating in Sichuan province in recent years were mainly LX4 genotype, which is the predominant genotype circulated in China in recent years.     

Sequence analysis of the gene coding for the S1 glycoprotein of infectious bronchitis virus (IBV) strains from New Zealand

Four new infectious bronchitis virus (IBV) strains (T6, K32, K43, and K87) were isolated from clinically infected chickens in New Zealand. These strains were compared with four strains (A, B, C, and D), which had circulated 25 years previously, by sequencing the gene coding for the S1 subunit of the spike glycoprotein. Analysis of the nucleotide and deduced amino acid sequences revealed that the eight strains from New Zealand are genetically related and share greater than 82.8% nucleotide and 79% amino acid homology within the S1 region. Strains T6, K43, and K87 were more than 99% homologous to previously described strains C and D. A fourth new strain (K32) was most closely related to the previously described B strain. Phylogenetic analysis of strains revealed that New Zealand strains were more closely related to Australian than European or North American strains. The New Zealand A strain shared 99.5% nucleotide and 98.7% amino acid homology with the Australian Vic S strain. Deduced amino acid sequence of the S1 glycoprotein indicated differences between strains that were, in general, consistent with virus neutralization patterns. The nucleotide sequence data reported in this article have been submitted to the GenBank nucleotide sequence database and have been assigned the accession numbers A = AF151953, B = AF151954, C = AF151955, D = AF151956, K32 = AF151957, K43 = AF151958, K87 = AF151959, and T6 = AF151960.     

Challenge experiments to evaluate cross-protection induced at the trachea and kidney level by vaccine strains and Belgian nephropathogenic isolates of avian infectious bronchitis virus

Intravenous and aerosol challenge experiments were conducted to evaluate tracheal and renal cross-protection in chickens immunized either with infectious bronchitis virus vaccine strains or with nephropathogenic infectious bronchitis virus (NIBV)-isolates. Intravenous challenge was carried out with four Belgian NIBV-isolates and with the Italian NIBV-strain AZ23.74. Virus titrations of tracheas collected at different times after aerosol challenge with the Belgian reference NIBV-strain B1648 demonstrated that only chickens immunized with the serologically closely related Belgian NIBV-field isolates showed strong trachea protection. The three vaccine strains H120, H52 and D274 and the heterologous NIBV-strain AZ23.74 did not induce protection of the respiratory tract against B1648. However, immunization with the latter strains shortened the period of replication of the challenge virus in the trachea. All chickens immunized with NIBV were strongly protected against nephritis after challenge with a homologous or heterologous NIBV-isolate. Vaccination with H52 gave partial kidney protection against NIBV challenge. Vaccination with H120 or D274 did not reduce kidney infection after NIBV challenge, as demonstrated by the incidence of mortality and kidney-immunofluorescence. Protection of the kidney was similar whether the challenge was performed intravenously or by aerosol. The results of both challenge experiments show that the development of a vaccine strain based on the Belgian NIBV-serotype is indicated to control NIBV in Belgian broiler flocks.     

Naturally occurring recombination between distant strains of infectious bronchitis virus

New variants of infectious bronchitis virus (IBV) have emerged in Australia despite its geographical isolation and intensive vaccination programs. In the present study, the 3′ terminal 7.2 kb of the genome of a recently isolated variant of IBV (N1/03) was sequenced and compared with the sequences of classical and novel strains of IBV, the two main groups of these viruses in Australia. The comparison revealed that recombination between classical and novel IBVs was responsible for the emergence of the new variant. It was concluded that novel IBVs, which have not been detected since 1993, and which are phylogenically more distant from classical IBVs than turkey coronaviruses, might still be circulating and contributing to the evolution of IBV in Australia.     

Serological relationship among ten strains of avian infectious bronchitis virus

Ten strains of avian infectious bronchitis virus (IBV) were studied serologically by cross-neutralization test using rabbit and chicken immune sera. With the chicken sera all 10 IBV strains were antigenically related. In particular, anti-KH serum neutralized all heterologous strains except of the Ishida strain; Nerima strain was neutralized by all antisera except of anti-Ishida serum. Most cross-reactions were less or more heterologous, thus all 10 IBV strains seemed to belong to one serological type. Using rabbit sera, all strains except of Connecticut A-5968, cross-reacted with certain other strains. Most cross-reactions were partially heterologous showing one-way-relationship; heterologous relations were observed less frequently than with chicken sera.     

Different genotypes of nephropathogenic infectious bronchitis viruses co-circulating in chicken population in China

Chicken nephropathogenic infectious bronchitis (IB) was prevalent in the most chicken farms during recent years, although the IB vaccination program has been widely performed in China. To characterize the S1 protein of infectious bronchitis virus (IBV) from China, five representative nephropathogenic IB viruses isolated from chickens in different provinces were genetically and phylogenetically analyzed. The results showed that the length of the S1 genes of the isolates were quite different (1,617, 1,620, 1,623, 1,629, and 1,632 nucleotides, respectively). The homology of the nucleotides and amino acids among the five isolates were 76.7% ∼ 92.1% and 73.9% ∼ 89.5%, respectively, indicating a great variation in S1 genes of the isolates. The variation in S1 genes might affect the antigenicity and pathogenicity of the viruses. Genetically, point mutations, insertions, and deletions in the S1 protein can be observed at many positions, especially at the first 150 amino acids in the N-terminal of the S1 protein. Two motif cleavage sites (R-R-X-R-R/S, H-R-R-R-R/S) were observed in the five sequenced strains. Phylogenetic analysis suggested that they belonged to different lineages. These findings indicated that different genotypes of nephropathogenic IB viruses were co-circulating in the chicken population in China.     

Combined infectious bronchitis virus Arkansas and Massachusetts serotype vaccination suppresses replication of Arkansas vaccine virus

Polyvalent infectious bronchitis virus vaccination is common worldwide. The possibility of vaccine interference after simultaneous combined vaccination with Arkansas (Ark) and Massachusetts (Mass)-type vaccines was evaluated in an effort to explain the high prevalence of Ark-type infectious bronchitis virus in vaccinated chickens. Chickens ocularly vaccinated with combinations of Ark and Mass showed predominance of Mass vaccine virus before 9 days post-vaccination (DPV) in tears. Even when Mass and Ark vaccines were inoculated into separate eyes, Mass vaccine virus was able to outcompete Ark vaccine virus. Although Mass vaccine virus apparently had a replication advantage over Ark vaccine in ocular tissues, Ark vaccine virus appeared to have an advantage in spreading to and/or replicating in the trachea. When chickens vaccinated with Ark or Mass vaccine were housed together, Mass vaccine virus was able to spread to Ark-vaccinated chickens, but the Ark vaccine was not detected in Mass-vaccinated chickens. Only Mass vaccine was detected in tears of sentinel birds introduced into groups receiving both vaccines. Furthermore, Ark vaccine virus RNA was not detectable until 10 DPV in most tear samples from chickens vaccinated with both Ark and Mass vaccines at varying Ark vaccine doses, while high concentrations of Mass virus RNA were detectable at 3–7 DPV. In contrast, Ark vaccine virus replicated effectively early after vaccination in chickens vaccinated with Ark vaccine alone. The different replication dynamics of Ark and Mass viruses in chickens vaccinated with combined vaccines did not result in reduced protection against Ark challenge at 21 DPV. Further studies are needed to clarify if the viral interference detected determines differences in protection against challenge at other time points after vaccination.